1. Field of the Invention
The present invention relates to a pipette system including a syringe having a mounting part and a syringe plunger, and hand pipette having means for receiving the syringe mounting part and means cooperating with the syringe plunger.
2. Description of the Prior Art
Pipette systems of the type referred to at the beginning often are defined as repeating or multipipette systems which allow the gradual delivery of a liquid from a syringe. Such a repeating pipette system is known from the DE-C2 29 26 691 which especially is directed to the repeating mechanism of the repeating pipette. It also describes how to secure a syringe of the system to said repeating pipette. For this purpose, the syringe is provided with a syringe flange adapted to be inserted from the side into a substantially U-shaped groove being open at the side. An axial pressure spring secures the inserted syringe flange to the nut. For the connection of the syringe plunger to a plunger adjusting means an insertion element is provided which receives an end section of the syringe plunger between two jaws. The jaws can be pressed against said syringe plunger by means of a flap-like clamping element, the actuating lever of which projects from the body through an opening. This way of fixing the syringe has the disadvantage that the syringe needs to be touched for inserting it and connecting the plunger adjusting means. There, however, are made high demands on the cleanness of the syringe. It is already manufactured on clean-room conditions and usually needs to be sterile. The syringe also needs to be touched when taking out the liquid which may involve a risk as a result of any adherent liquid.
From the CH 671 526 A5 and the EP 0 226 867 A2 a pipette system has become known comprising a syringe which, with the syringe flange and the syringe plunger, is axially movable in positions of attachment of accommodations. Therefore, fastening means in the form of first gripping means and second gripping means with slotted end sections are provided which are snapped on the flange of the syringe body and an annular portion of the syringe plunger. For this purpose, the syringe body first is inserted into the first gripping means and then the second gripping means is moved so as to snap on the pipette plunger. After pipetting the syringe is ejected by first pressing the syringe body out of the end section of the pipette by moving forward the second gripping means and, by moving forward said end sections of the second gripping means still further, causing it to expand by an expanding sleeve and release the plunger of the syringe.
According to this automatic device, the elastic restoring forces of the slotted end sections need to be overcome for fastening or detaching the syringe. Said slotted end sections need to be big enough to prevent the syringe from completely or partly slipping from its attachment when drawing in or delivering a liquid. Besides, the syringe can only be inserted and ejected with the plunger of the syringe being completely pressed in because the second gripping means are required to move forward towards the syringe in both cases.
The U.S. Pat. No. 4,616,514 and the WO 93/15837 also relate to systems comprising self-elastic coupling elements.
Taking all this as a basis, it is the object of the invention to provide a pipette system for manual operation which allows an easier and more reliable connection of the syringe to the pipette and an easier separation of the syringe from the pipette without having to be touched by the user and which offers an enlarged range of application.
SUMMARY OF THE INVENTION of the object of the invention is achieved by providing fastening means for releasably connecting the syringe and the pipette which fastening means comprises manually operated and radially displaceable gripping levers.
According to an inventive pipette system, the flange receiving means and plunger receiving means are provided with one axial opening each. The syringe with its mounting part and syringe plunger can be moved axially only through the axial openings directly to the positions of attachment of said mounting part and syringe plunger. The mounting part and syringe plunger are secured by radially movable gripping means which e.g. grip a syringe flange of the syringe and a plunger collar of the syringe plunger in the positions of attachment. With these features of the pipette system it is achieved that the syringe and hand pipette can be interconnected by an all-axial relative movement and can be separated from each other by an actuation of the fastening means. Thereat the syringe may be held in a stationary position, for instance within a mount, so that the connection and separation process requires manipulations of the hand pipette only. As a result of the axial movement the gripping means can be controlled automatically when the syringe and the hand pipette are connected to each other. Needless to say that the syringe can also be ejected by loosening the fastening means, for instance under the influence of gravity. In any case, the connection and separation of the syringe and hand pipette does not make any manipulation of the syringe necessary any longer. Thus, a contamination of the syringe and the user practically are impossible. Preferably, the pipette system is carried out as a repeating pipette system.
The axial arrangement of the gripping means allows the latter, irrespective of a spring resistance to be overcome during insertion, to positively and hence safely hold the syringe in the positions of attachment of said mounting part and said syringe plunger. The spring resistances can be selected user-optimized is spring means are forcing the gripping means into the position of attachment. Moreover, the axially arranged gripping means, on principle, can be activated regardless of the axial position of the displaceable receiving body within the pipette body so that completely or partly filled syringes can be secured to the hand pipette or separated therefrom. Thus, according to the invention, a pipette system had been provided which, especially, supports the manual operation and enlarges the range of application.
Preferably, the mounting part or syringe in its receiving abuts against abutments and is fixed thereto by the gripping means by engaging it round. Therefor the mounting part may comprise a syringe flange while the plunger may comprise a plunger collar. Furthermore, the gripping means may be gripping levers. The syringe gripping lever may comprise a hook-shaped gripping end for engaging round the mounting part. Plunger gripping levers having a wedge-shaped gripping end preferably are provided for engaging round a plunger. Said gripping levers may be double-armed and comprise one gripping arm as well as one operating arm.
Spring means may force the gripping means into the locking position. Syringe gripping levers then may be forced into their locking position by means of stationary leaf springs. For the plunger gripping levers leg springs may be provided which are arranged on a pivoted axis of said levers and with one leg they press against the receiving body while with the other leg they press against the plunger gripping lever. The arrangement of the syringe gripping levers or plunger gripping levers in radial breakthroughs of the pipette body or receiving body facilitate their actuation from outside. For this purpose, the syringe gripping levers may have operating arms adapted to be activated from outside. These operating arms may be provided with points of contact inside, e.g. release cams, which can be pivoted towards the operating arms of the plunger gripping levers for activating them.
To allow a compensation of tolerances and an automatic ejection of the syringe when loosening the fastening means the abutment for the mounting part may be supported by axially operating spring means in the pipette body.